201215682 六、發明說明： 【發明所屬之技術領域】 本發明係關於一種將以旋轉爐床式爐 製造之粒狀金屬鐵於電弧爐令炫解 還原炫融爐所 【先前技術】 &熔鋼之方法。 製鋼用電弧爐，以往係採用如下方法.、 桶將廢料、生鐵（冷生鐵）、還原鐵等鐵原H料（scrap) 入爐内，熔解後打開爐蓋將上述鐵 八…、上分批裝 其炼解。因此，於爐蓋打開及鐵原料裝Z追加裝入並使 量損失及時間損失、以及大量粉塵：4間’會產生熱 惡化的問題。 讀塵飛散至爐外之作業環境 其對策係連續投入成分與尺寸相 — 如參照專利文獻1〜3)，但由於還原鐵原鐵（例 原之氧化鐵，故而存在較廢料或生=脈石成分或未還 炼解能量之問題。 次生鐵（冷生鐵）…多 另一方面，關於生鐵（冷生鐵），因製造上之問題而有 無法減小尺寸之限制，無法實現藉由連續投入之大量投 入、熔解。 又:為提高製鋼用電弧爐之生產性’氧合操作固定， 氧使用里亦立曰力〇與投入氧量相平衡之碳源之使用量亦增 加0 該碳源係使㈣生鐵或冷生鐵中之碳分、塊狀焦炭、 焦炭粉等。 然而’於使用以鐵之情形時，存在於製鋼帛電孤爐201215682 VI. Description of the invention: [Technical field of the invention] The present invention relates to a granular metal iron manufactured by a rotary hearth furnace in an electric arc furnace to reduce the brightness of the melting furnace [Prior Art] & The method. In the past, the electric arc furnace for steelmaking used the following method. The barrel was used to scrape scrap, raw iron (cold iron), reduced iron and other iron raw materials into the furnace. After melting, the furnace cover was opened to separate the above-mentioned irons. Install it for refining. Therefore, there is a problem that the furnace cover is opened and the iron material Z is additionally loaded and the amount of loss and time is lost, and a large amount of dust is generated. In the working environment where the dust is scattered to the outside of the furnace, the countermeasure is to continuously input the components and the size phase - as described in Patent Documents 1 to 3, but due to the reduction of the iron iron (the original iron oxide, there is a waste or raw = gangue). The problem of the composition or the energy of the secondary energy. Secondary iron (cold iron)... On the other hand, regarding pig iron (cold iron), there is a limit to the manufacturing problem and it is impossible to reduce the size. A large amount of input and melting. In addition, in order to improve the productivity of the electric arc furnace for steelmaking, the oxygenation operation is fixed, and the amount of carbon source used in the balance of oxygen and the amount of input oxygen is also increased by 0. (4) Carbon, pig coke, coke powder, etc. in pig iron or cold pig iron. However, when using iron, it exists in steelmaking furnace
S 4 201215682 之上游側需要炼生鐵之專用製造設備及專用裝入電弧 之設備的問題。 另-方面，於使用冷生鐵之情形時，如上所述，由於 其尺寸較大故而僅限於分批裝人、4解時耗㈣間，故 有限制政用量的問題。 又，於使用塊狀焦炭、焦炭粉之情形時，存在如 使用量受到全部含硫量及含灰量之組成的限制；由於 =入電弧爐巾時經料捕獲，或排氣之㈣排出至爐外故 而添加良率下降等。 、此處’開發出如下方法：將含有碳質還原材料與含氧 ^鐵之物質的原料於旋轉爐床式爐等還㈣融爐内加执， 使該原料中之氧化鐵固體還原後，對生成之金屬鐵進」步 口熱並使其溶融，並且一面使其與炼渣成分分離一面凝 It此製造高純度之粒狀金屬鐵（例如參照專利文獻4、 若將該粒狀金屬鐵與叆馬雜 一孰興還原鐵相比較’由於預先去除熔 刀、’且可提巧含碳量，故而藉由代替還原鐵連續裝入 電弧爐中而期待併用氣洛—池 、 解能量，並且二::煉從而大幅減少電弧爐中之炫 杈同熔鋼之生產性。 有效製鋼用電弧爐中連續裝人該種粒狀金層鐵更 有效進仃熔解之技術至今尚未建立。 專利文獻1 :曰本特開昭50 — 641 1 1號公報 專利文獻2 :日本特開昭5 1 — 65007號公報 專利文獻3 :日本特開昭58 — 141314號公報 201215682 專利文獻4 :曰太姓p日 口尽特開2002- 339009號公報 專利文獻5 :日太姓日日。Λ Λ。 口尽特開2003 - 73722號公報 【發明内容】 因此，本發明之曰μ 4 , 的在於提供—種在將以旋轉爐床式 爐4還原炼融爐所贺# + ^β ^ ^ 表w之粒狀金屬鐵連續裝入製鋼用電弧 爐中並熔解而製造炫:相^主 ^ , 塔鋼時，可更有效地熔解之熔鋼製造方 法。 本發明提供一種使用以下粒狀金屬鐵之熔鋼製造方 法。 (1) 一種使用粒狀金屬鐵之熔鋼製造方法，包括將由 粒狀金屬鐵與其他鐵原料所構成之總裝入鐵原料於電弧爐 中熔解之步驟，該粒狀金屬鐵係藉由包括下述步驟之方法 製付.將含有碳質還原材料與含氧化鐵之物質的原料於還 原熔融爐内加熱，並使該原料令之氧化鐵固體還原而生成 金屬鐵之步驟，及進一步加熱所生成之金屬鐵並使其熔 融，且一面使其與熔渣成分分離一面凝聚之步驟，其特徵 在於： 將上述粒狀金屬鐵中之碳含量設為1.0〜4·5質量％，並 藉由併用氧氣吹煉而使上述粒狀金屬鐵中之碳燃燒，且 將上述粒狀金屬鐵相對於上述總裝入鐵原料之使用比 例設為40〜80質量％ ’並於將上述其他鐵原料初始裝入上 述電弧爐而製成熔鐵後，於該熔鐵中連續地裝入上述粒狀 金屬鐵。 (2 )如（1 )之製造方法，其中，將每1 MW投入電力 201215682 述粒狀金屬鐵之裝入速度設為40〜100 kg/min/ MW。 (3) 如（1)或（2)之製造方法，其中，將上述粒狀 金屬鐵於熔鐵表面夕# . 取衣面之裝入位置設於電極節圓（electrode pitch circle)内。 (4) 如（1)至（3)中任一項之製造方法，其中，使 上述粒狀金屬鐵之平均粒徑為1〜50 mm。 (5) 如（1)至中任一項之製造方法，其中，一 面，形成於上述炫鐵上之溶融溶渣層成形而一直將電極之 知包覆 面於上述熔鐵中連續地裝入上述粒狀金屬鐵。 _ ( 6 )如（1 )至（5 )中任一項之製造方法，其中，在 、〃卩至㊉/直下，將以上述還原熔融爐製造之粒狀金屬鐵 於400〜700t連續地裝入上述電弧爐之熔鐵中。 根據本發明，藉由將以還原熔融爐製造之含碳量1.0〜 4.5質量％之減金屬鐵併用t氣吹煉而使上述粒狀金屬鐵 中之碳燃燒，且相對於總裝入鐵原料使用4〇〜8〇質量％， 並將其連續地裝入其他鐵原料初始裝入電弧爐中而製成的 熔生鐵中，藉此可實現大幅降低熔解能量且使電弧爐之能 量效率上升，並且使熔鋼之生產性大幅提高。 【實施方式】 以下，根據圖式，對本發明之實施形態進行詳細說明。 [實施形態1] 圖1表示本發明之一實施形態之熔鋼製造設備的概略 構成。本實施形態之設備係作為還原熔融爐之旋轉爐床式 201215682 爐1與電弧爐2接近設置時之例。 並且，本發明中所使用之粒狀金屬鐵A係以例如以下 之方法而製造。 首先，使含有煤等碳質還原材料及鐵礦石等含氧化鐵 之物質的原料塊狀化成顆粒或壓塊（briquette )。並且，將 該塊狀化物載置於底鋪有碳材C之未圖示之爐床上，於旋 轉爐床式爐1内例如加熱至1350〜1400。(：左右，而使原料 中之氧化鐵固體還原後’進一步將所生成之金屬鐵加熱至 1400〜1550°C左右而使其熔融，並且一面使其與溶潰成分 分離一面凝聚。此後’於爐内之冷卻部冷卻至1〇〇〇〜丨1〇〇 °C左右’藉此獲得固化之粒狀金屬鐵a與熔渣b的混合物。 並且，將該混合物與底鋪碳材C 一併自旋轉爐床式爐丨中 排出後，使用篩網3及磁選機4將熔渣B與底鋪碳材c分 離去除，藉此獲得粒狀金屬鐵A (例如參照上述專利文獻i 3 °其内谷作為參照而併入本文中）。 將該粒狀金屬鐵A中之含碳量設為1〇〜4 5質量 各反量之下限设為1 〇質量％之原因在於， 之鋼之種類的必要C量，提高作為鐵原料之通用2 = 方=’將含碳量之上限設為4·5 f量％之原因在於，不加重 '反處理等附加處理之負荷而使用。粒狀金屬鐵A中之含 ::,較佳範圍為15〜3 5質量％。粒狀金屬鐵A中之含 :曰。由調節上述塊狀化物中之碳質還原材料之調配量 S旋轉爐床式爐1内之氣體環境而容易地調整。 在此，於旋轉爐床式爐i内，粒狀金屬鐵A處於溶融 8 201215682 狀態時’該粒狀金屬鐵A中之碳由於易於聚集於該粒狀金 屬鐵A之表面附近’故而固化後之粒狀金屬鐵a亦越靠近 其表面附近碳濃度越高。因此，裝入電弧爐2之熔鐵f中 的粒狀金屬鐵A容易自碳濃度高之低溶點的表面附近開始 炼解。該炼解之高碳漢度溶鐵中之碳藉由併用氧氣吹煉， 即藉由對電弧爐2内吹入氧’而由於該氧會燃燒，藉由其 燃燒熱會使粒狀金屬鐵A内部之碳濃度較低之高熔點部分 亦容易地炼解。 將該粒狀金屬鐵A與作為其他鐵原料之廢料D組合製 成總裝入鐵原料，並使粒狀金屬鐵A相對於該總裝入鐵原 料之使用比例為4 0〜8 0質量％。 並且’首先將廢料D初始裝入（分批裝入）電弧爐2 中’利用電極7電弧加熱熔解而製作熔鐵ρ。 此後’一面繼續進行電弧加熱，一面吹入氧（視需要 進而吹入煤粉），並於該熔鐵F中連續地裝入粒狀金屬鐵a 並使其溶解’藉此可提高電弧爐2之能量效率且提高炫鋼g 之生產性’更有效地獲得熔鋼G。 此處’使粒狀金屬鐵A相對於總裝入鐵原料之使用比 例為40〜80質量％之原因在於根據如下理由。 即’採用實際運行之電弧爐（内容量：90 t，變壓器容 量：74 MVA)為例，估算對因粒狀金屬鐵之使用比例、裝 入方法之差異而引起之熔解總裝入鐵原料所需之熔解能 量、及熔鋼之生產速度造成的影響。 此處，使粒狀金屬鐵之含碳量為2.5質量％。又，「分 201215682 批裝入」及「連續裝入」粒狀金屬鐵時之粒狀金屬鐵的溫 度设為常溫（2 5 C )，「向溫連續裝入」時之粒狀金屬鐵的 溫度設為400°C。又，藉由將粒狀金屬鐵自「分批裝入」變 更為「連續裝入」，而使每1次追加裝入之爐之熱量損失減 少870 Meal (此處1 Meal = 4.18605 MJ，以下相同），斷電 時間縮短2 min，鑽孔時間亦縮短2 mjn。 估算之結果示於圖2及圖3。圖2係表示因粒狀金屬鐵 之使用比例、裝入方法之差異而引起之熔解總裝入鐵原料 所需之溶解能量的變化者。又，圖3係表示因粒狀金屬鐵 之使用比例、裝入方法之差異所引起之熔鐵生產速度的變 化者。 若粒狀金屬鐵A之使用比例未達40質量％，即，作為 其他鐵原料之廢料D之使用比例超過60質量％，則由於用 以分批裝入之未圖示之廢料桶的容量限制，初始裝入廢料D 必須分為2次進行，如圖3所示，即便連續裝入粒狀金屬 鐵A熔鋼生產速度亦大幅下降。 另一方面’若粒狀金屬鐵A之使用比例超過80質量％， 則於「高溫連續裝入」粒狀金屬鐵A之情形時，由於脫碳 時間較由電弧爐2之投入電力容量所決定的炼解時間增 長’且該脫碳時間對炼鋼之生產性限速，故而如圖3所示， 炫鋼生產速度之上升達到頂點。 根據以上結果’使粒狀金屬鐵A相對於總裝入鐵原料 之使用比例為4 0〜8 0質量％。 又’每1 MW投入電力之粒狀金屬鐵A的裝入速度根On the upstream side of S 4 201215682, there is a need for special manufacturing equipment for refining iron and equipment for special arc loading. On the other hand, in the case of using cold pig iron, as described above, since it is large in size, it is limited to batch loading, and time (4), so there is a problem of limiting the amount of government. Moreover, in the case of using block coke or coke powder, there is a limitation that the amount of use is affected by the composition of all sulfur content and ash content; since it is captured by the electric arc furnace, or discharged (4) The outside of the furnace is added and the yield is lowered. Here, 'the following method has been developed: a raw material containing a carbonaceous reducing material and a substance containing oxygen and iron is added to a rotary hearth furnace or the like (4), and the iron oxide solid in the raw material is reduced. The generated metal iron is heated and melted, and is separated from the slag component to form a high-purity granular metal iron (for example, refer to Patent Document 4, if the granular metal iron is used) Compared with the 叆 杂 孰 孰 还原 还原 ' ' 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于 由于And the second:: refining greatly reduces the productivity of the sleek and molten steel in the electric arc furnace. The technology for continuously charging the granular gold layer iron in the effective electric arc furnace has not been established yet. 1 : 曰 特 昭 50 — — — — 50 50 50 50 50 50 50 50 50 50 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 The day of the mouth is open to the special 2002-339009 Patent Document 5: Japanese name, Japanese name, 日 Λ. 尽 特 2003 2003-73722 SUMMARY OF THE INVENTION Therefore, the present invention is based on the provision of a rotary hearth furnace 4 Reducing the smelting furnace to the ##^^^^^ The granular metal iron of the table w is continuously loaded into the electric arc furnace for steelmaking and melted to produce a dazzle: when the steel is used, the molten steel can be melted more efficiently. The present invention provides a method for producing a molten steel using the following granular metal iron. (1) A method for producing a molten steel using granular metallic iron, comprising a total iron-filled iron composed of granular metallic iron and other iron raw materials. a step of melting a raw material in an electric arc furnace, wherein the granular metallic iron is produced by a method comprising the steps of: heating a raw material containing a carbonaceous reducing material and an iron oxide-containing material in a reduction melting furnace, and heating the raw material a step of reducing the iron oxide solid by the raw material to form metallic iron, and further heating and melting the generated metallic iron, and separating the molten iron component while being separated from the molten slag component, wherein the granular metal is Carbon in iron The content is set to 1.0 to 4.5% by mass, and the carbon in the granular metallic iron is burned by blowing with oxygen, and the ratio of the above-mentioned granular metallic iron to the total charged iron raw material is set to 40. ～80% by mass', after the other iron raw material is initially charged into the electric arc furnace to form a molten iron, the granular metal iron is continuously charged into the molten iron. (2) Manufacturing method as (1) In the above, the charging rate of the granular metal iron is set to be 40 to 100 kg/min/MW per 1 MW of the electric power. The metal iron is on the surface of the molten iron. The loading position of the take-up surface is set in the electrode pitch circle. The manufacturing method according to any one of (1) to (3) wherein the granular metal iron has an average particle diameter of 1 to 50 mm. (5) The method according to any one of (1), wherein the molten slag layer formed on the glazed iron is formed, and the coated surface of the electrode is continuously loaded into the molten iron. The above granular metal iron. The manufacturing method of any one of (1) to (5), wherein the granular metal iron manufactured by the above-mentioned reduction melting furnace is continuously loaded at 400 to 700 tons at a temperature of from ten to ten. Into the molten iron of the above arc furnace. According to the present invention, the carbon in the granular metal iron is burned by blowing the metal iron having a carbon content of 1.0 to 4.5% by mass in a reduction melting furnace and blowing it with t gas, and is used in comparison with the total iron raw material. 4 〇 to 8 〇 mass%, and continuously loaded into the molten iron prepared by initially charging other iron raw materials into the electric arc furnace, whereby the melting energy can be greatly reduced and the energy efficiency of the electric arc furnace is increased, and The productivity of molten steel is greatly improved. [Embodiment] Hereinafter, embodiments of the present invention will be described in detail based on the drawings. [Embodiment 1] Fig. 1 shows a schematic configuration of a molten steel manufacturing facility according to an embodiment of the present invention. The apparatus of the present embodiment is an example in which the rotary hearth type 201215682 furnace 1 of the reduction melting furnace is placed close to the electric arc furnace 2. Further, the granular metallic iron A used in the present invention is produced, for example, by the following method. First, a raw material containing a carbonaceous reducing material such as coal or an iron oxide-containing material such as iron ore is formed into a pellet or a briquette. Further, the bulk material is placed on a hearth (not shown) on which the carbon material C is placed, and heated in the rotary hearth furnace 1 to, for example, 1350 to 1400. (: Left and right, and after the iron oxide solid in the raw material is reduced, 'the metal iron to be produced is further heated to about 1400 to 1550 ° C to be melted, and is separated from the molten component while being agglomerated. The cooling portion in the furnace is cooled to about 1 〇〇〇 1 〇〇 1 ° ° C to thereby obtain a mixture of the solidified granular metal iron a and the slag b. Further, the mixture is combined with the underlying carbon material C. After being discharged from the rotary hearth furnace, the slag B and the underlying carbon material c are separated and removed using the screen 3 and the magnetic separator 4, whereby the granular metallic iron A is obtained (for example, refer to the above patent document i 3 ° The inner valley is incorporated herein by reference.) The carbon content in the granular metallic iron A is set to 1 〇 to 45. The lower limit of each inverse of the mass is set to 1 〇 mass% because the type of steel The amount of necessary C is increased as the general purpose of the iron raw material. 2 = square = 'The upper limit of the carbon content is set to 4·5 f. The reason for the use is that the load of the additional treatment such as the reverse treatment is not emphasized. The content of iron A::, preferably in the range of 15 to 35 mass%. The content of the granular metal iron A: 曰. The amount of the carbonaceous reducing material in the above-mentioned bulk compound is adjusted to be easily adjusted by rotating the gas atmosphere in the hearth furnace 1. Here, in the rotary hearth furnace i, the granular metallic iron A is melted 8 In the state of 201215682, the carbon in the granular metallic iron A is easily aggregated near the surface of the granular metallic iron A. Therefore, the granular metal iron a which is solidified is also closer to the surface thereof, and the carbon concentration is higher. The granular metallic iron A in the molten iron f of the electric arc furnace 2 is easily decomposed from the vicinity of the surface of the low melting point where the carbon concentration is high. The carbon in the molten iron of the high carbon black is melted by using oxygen together. That is, by blowing oxygen into the electric arc furnace 2, since the oxygen is burned, the high melting point portion having a low carbon concentration inside the granular metallic iron A is easily refining by the heat of combustion. The granular metal iron A is combined with the waste material D as another iron raw material to form a total iron raw material, and the use ratio of the granular metal iron A to the total iron raw material is 40 to 80% by mass. Initially loading (distributing) the waste D into the electric arc furnace 2 The electrode 7 is heated by electric arc melting to produce a molten iron ρ. Thereafter, while continuing the arc heating, oxygen is blown in (when the coal powder is blown if necessary), and the granular metallic iron a is continuously charged into the molten iron F. By dissolving it, the energy efficiency of the electric arc furnace 2 can be increased and the productivity of the steel g can be improved, and the molten steel G can be obtained more efficiently. Here, the ratio of the use of the granular metallic iron A to the total charged iron raw material is The reason of 40 to 80% by mass is based on the following reasons: 'Using the actual operation of the electric arc furnace (content amount: 90 t, transformer capacity: 74 MVA) as an example, estimating the proportion of the use of granular metal iron, loading method The difference caused by the melting causes the total melting energy required for the iron raw material and the production speed of the molten steel. Here, the carbon content of the granular metal iron was 2.5% by mass. In addition, the temperature of the granular metallic iron when the batch is filled with the granular metal iron in the "201215682 batch loading" and the "continuous loading" of the granular metallic iron is set to normal temperature (25 C), and the granular metallic iron in the "continuous loading into the temperature" The temperature was set to 400 °C. In addition, by changing the granular metal iron from "batch loading" to "continuous loading", the heat loss per furnace is reduced by 870 Meal (here 1 Meal = 4.18605 MJ, below) The same), the power-off time is shortened by 2 min, and the drilling time is also shortened by 2 mjn. The results of the estimation are shown in Figures 2 and 3. Fig. 2 is a graph showing changes in the dissolved energy required for melting the total iron raw material due to the difference in the use ratio of the granular metallic iron and the charging method. Further, Fig. 3 shows a change in the production speed of the molten iron due to the difference in the use ratio of the granular metallic iron and the charging method. If the use ratio of the granular metal iron A is less than 40% by mass, that is, the use ratio of the waste D as the other iron raw material exceeds 60% by mass, the capacity limit of the waste drum (not shown) for batch loading is limited. The initial loading of waste D must be carried out in two stages, as shown in Fig. 3, even if the continuous loading of granular metal iron A molten steel production speed is greatly reduced. On the other hand, if the use ratio of the granular metallic iron A exceeds 80% by mass, the decarburization time is determined by the electric power capacity of the electric arc furnace 2 when the granular metal iron A is continuously charged at a high temperature. The refining time increases' and the decarburization time limits the productivity of steelmaking. Therefore, as shown in Fig. 3, the increase in the production speed of Hyungang reaches its peak. According to the above result, the ratio of use of the particulate metallic iron A to the total iron-containing raw material is 40 to 80% by mass. In addition, the loading rate of granular metal iron A per 1 MW of input power
S 10 201215682 據乂下理由，較佳為設為〜⑽min/ Mw。 即’為掌握連續裝入時之粒狀金屬鐵的熔解特性，使 用具有下述表丨所示之物理、化學性狀的粒狀金屬鐵及作 為比較材料的還原鐵作為熔解鐵原料而實施熔解試驗。 表1] 視密度 (g/cm2) 粒徑 (mm) 2.4 〜2·5 成分（質量％) T.Fe M.Fe FeO C - > 95.0 1.5 〜3.0 92.5 85.6 6.3 0.4 〜0.8 2.8' <熔解鐵ST 之種類 粒i金屬Ϊ —還原涵Γ 料熔解試驗裝置’如圖4所示之概略構成，使用由 如下機構所構成者：5〇〇 kg之高頻感應爐（定額：35〇 kw、 woohz)、原料供給裝置（料斗容量：2〇〇kg，原料投入速 又·〜 g/min)、用以觀察熔解狀況的監控用攝影機、 以及用以兄錄溶液溫度及原料投入速度的資料收錄裝置。 作為熔解條件：製作C : 0.2〜0.3質量％、Si < 0.03質 里/〇、Mn . 〇.05質量°/〇、溫度：155(TC之初始熔液250 kg， 一面將熔液溫度維持在155〇〜16〇〇〇c , 一面依序改變原料 投入速度，並一面以監控用攝影機確認連續裝入之鐵原料 順利地熔解，一面調整投入電力。 溶解武驗之結果示於圖5及下述表2。 201215682 [表2] 熔解之模式 鐵原料裝 入速度 (kg/min ) 投入電 力 (kW) 最大溶解速度 [R] (kg/min/MW ) 修正後之最大溶解速度 [R']=[R]/[C]xio〇 (kg/min/MW) 初始溶液之 溫度維持 0.0 78 - 0.0 79 - 一 0.0 80 - 粒狀金屬鐵 之連續熔解 0.0 80 - __ 4.0 205 32.0 ------ 62.4 4.0 225 27.6 7.0 318 29.4 46.9 7.0 330 28.0 44 7 還原鐵之 連續熔解 1.5 220 10.7 1.8 250 10.6 一 2.0 250 11.8 - 如該等圖表所示，粒狀金屬鐵相較於還原鐵，每1 Mw 投入電力之最大熔解速度為2·5〜3.0倍。 再者，如此粒狀金屬鐵之最大熔解速度成為還原鐵之 最大熔解速度的2.5〜3.0倍，只要還原鐵中所含之熔渣成 分的量與粒狀金屬鐵相比更多即可，無法說明，一般認為 其原因在於作為熔解試驗之加熱源並非電弧加熱，而係使 用高頻感應加熱。 即，一般認為其原因在於：粒狀金屬鐵由於與熔鐵之 視密度大致相等故而以浮動於熔鐵中之狀態熔解，熔鐵則 藉由高頻感應加熱而被充分加熱，故而使粒狀金屬鐵之熔 解速度充分變大。另一方面，還原鐵由於與熔融熔渣之視 密度大致相等故而以浮動於熔融熔渣中之狀態熔解，而熔 融熔渣與電弧加熱相異，無法藉由高頻感應加熱來充分加 熱。因此，還原鐵之熔解速度與粒狀金屬鐵相比大幅下降。 此處，由於本熔解試驗裝置為5〇〇 kg之小型，故而與 12 201215682 實際運行之9Gtf弧爐相比熱量損失明 於將本熔解试驗中所得之粒狀金屬鐵之每1 MW投入電力 的最大'熔解速度用於實際i軍许夕^ 頁U運灯之電弧爐中之情形時，會進 一步變大。因此，以如下之方彳 下之方式推斷於將粒狀金屬鐵連續 裝入實際運行之90 t電狐爐中之_犯吐从， 电狐爐甲之If形時的粒狀金屬鐵之每i MW投入電力的熔解速度。 如下述表3所示’若求出本溶解試驗裝置中之粒狀金 屬鐵的熔解電力基本單位’於裝入速度為η〆—之情形 時獲得7M kWh/t，於裳入速度為7 W之情形時獲 得。另-方面，於上述實際運行之9〇t電狐爐 :’由於連續裝人還原鐵之情形時之料電力基本單位的 實際值存在，故而若於該還原鐵之熔解電力基本單位之實 際值中考慮還原鐵與粒狀鐵之成分差異而估算粒狀金屬鐵 之炼解電力基本單位’則獲得366 kWhe因此，本溶解試驗 裝置相對於上述實際運行之9〇 t電弧爐的投入電力效率係 如同一表格所示，於投入速度為4kg/min之情形時為366 /714=51.3%，於投入速度為7 kg/min之情形時為366/ 584= 62·70/〇。S 10 201215682 It is preferable to set it to ~(10)min/Mw for the following reasons. In other words, in order to grasp the melting characteristics of the granular metallic iron at the time of continuous charging, a molten metal iron having the physical and chemical properties shown in the following table and reduced iron as a comparative material were used as the molten iron raw material to carry out a melting test. . Table 1] Apparent density (g/cm2) Particle size (mm) 2.4 〜2·5 Component (% by mass) T.Fe M.Fe FeO C - > 95.0 1.5 ～3.0 92.5 85.6 6.3 0.4 〜0.8 2.8' < The type of molten iron ST is a high-frequency induction furnace of 5 〇〇kg (amount: 35〇kw). , woohz), raw material supply device (hopper capacity: 2〇〇kg, raw material input speed·~g/min), monitoring camera for observing the melting condition, and data for the temperature of the solution and the input speed of the raw material Recording device. As a melting condition: Preparation C: 0.2 to 0.3% by mass, Si < 0.03 mass / 〇, Mn. 〇.05 mass ° / 〇, temperature: 155 (TC initial melt 250 kg, while maintaining the melt temperature In 155 〇 to 16 〇〇〇 c, the raw material input speed was sequentially changed, and the continuously charged iron raw material was confirmed to be smoothly melted by the monitoring camera, and the input electric power was adjusted. The results of the dissolution test are shown in Fig. 5 and Table 2 below. 201215682 [Table 2] Melting mode Iron raw material loading speed (kg/min) Input power (kW) Maximum dissolution rate [R] (kg/min/MW) Corrected maximum dissolution rate [R' ]=[R]/[C]xio〇(kg/min/MW) The temperature of the initial solution is maintained at 0.0 78 - 0.0 79 - a 0.0 80 - continuous melting of granular metallic iron 0.0 80 - __ 4.0 205 32.0 --- --- 62.4 4.0 225 27.6 7.0 318 29.4 46.9 7.0 330 28.0 44 7 Continuous melting of reduced iron 1.5 220 10.7 1.8 250 10.6 a 2.0 250 11.8 - As shown in the graphs, granular metallic iron is compared to reduced iron, 1 Mw The maximum melting rate of input power is 2·5~3.0 times. Moreover, the maximum of such granular metal iron The melting rate is 2.5 to 3.0 times the maximum melting rate of the reduced iron, as long as the amount of the slag component contained in the reduced iron is more than that of the granular metallic iron, which cannot be explained, and is generally considered to be a melting test. The heating source is not an arc heating, but uses high frequency induction heating. That is, it is generally considered that the reason is that the granular metallic iron is melted in the molten iron due to the apparent density of the molten iron being substantially equal, and the molten iron is Since the high-speed induction heating is sufficiently heated, the melting rate of the granular metallic iron is sufficiently increased. On the other hand, the reduced iron is floated in the molten slag because it is substantially equal to the apparent density of the molten slag. Melting, and molten slag is different from arc heating, and cannot be sufficiently heated by high-frequency induction heating. Therefore, the melting rate of reduced iron is significantly lower than that of granular metal iron. Here, since the melting test device is 5 〇〇kg is small, so the heat loss compared with the actual running 9Gtf arc furnace of 201215682 is better than the 1 MW of the granular metal iron obtained in the melting test. The maximum 'melting speed of the incoming electric power is further increased when it is used in the actual electric arc furnace of the U-lights. Therefore, it is inferred that the granular metal iron is continuous in the following way. The melting rate of the electric power per MW of the granular metal iron in the case of the electric fox furnace is made into the actual operation of the 90-ton electric fox furnace. As shown in Table 3 below, 'If the basic unit of melting electric power of granular metal iron in the dissolution test apparatus is obtained, the loading speed is η〆-, 7M kWh/t is obtained, and the skirting speed is 7 W. Obtained when the situation arises. On the other hand, in the above-mentioned actual operation of the 9 〇t electric fox furnace: 'The actual value of the basic unit of the material power due to the continuous loading of the reduced iron, so if the actual value of the basic unit of the molten iron is dissolved Considering the difference between the composition of reduced iron and granular iron and estimating the basic unit of refining power of granular metal iron, 366 kWhe is obtained. Therefore, the input power efficiency of the dissolution test device relative to the above-mentioned 9〇t electric arc furnace is actually As shown in the same table, it is 366 / 714 = 51.3% at an input speed of 4 kg / min and 366 / 584 = 62 · 70 / 于 at an input speed of 7 kg / min.
[表3] - __J 熔解 原料 5G〇lcg高頻感應爐 901電弧爐 投入電力~ 效率[C] = [Β]/[Α]χ1〇〇 (%) 裝入速度 (kg/min ) 總裝入 量（kg) 總投入電 能(KWh) 電力基本 單位[A] (kWh/t) 電能 基本單位 [B] (KWh) 粒狀 _章屬鐵 4 29.13 h 20.8 714 366 51.3 7 72.62 42.4 584 366 62.7 13 201215682 此處，藉由將上述表2所示之本熔解試驗裝置中的粒 狀金屬鐵之每1 MW投入電力之最大熔解速度[R]除以上述 投入電力效率[C]/100而加以修正，並推斷上述實際運行 之90 t電弧爐中的粒狀金屬鐵之每1 MW投入電力之最大 熔解速度（參照上述表2之「修正後之最大熔解速度」欄）。 匯整上述推斷結果並示於下述表4之「連續裝入」欄 中。又，同一表格中，粒狀金屬鐵之含碳量設為2.5質量％， 分別針對藉由氧氣吹入而使該含有碳燃燒並賦予能量之情 形、進而於將粒狀金屬鐵於600°C下高溫裝入之情形估算上 述實際運行之90 t電弧爐中的電力基本單位，一併記錄對 粒狀金屬鐵之每1 MW投入電力之最大熔解速度進行推斷 的結果。 [表4] 電力基本單位 (KWh/t) 最大熔解速度 (Kg/min/MW) 連續裝入 366[基礎] 44 〜62 追加連續裝入+C燃燒 312 51 〜77 追加高溫連續裝入+C燃燒 230 70 〜98 根據上述表4所示之推斷結果，可知粒狀金屬鐵之每1 MW投入電力之最大熔解速度係根據該粒狀金屬鐵之含碳 量或裝入溫度而發生變動，但在40〜100 kg/ min/MW之 範圍。藉此，推薦將每1 MW投入電力之粒狀金屬鐵A的 裝入速度設為40〜100 kg/min/MW。 又，較佳為將粒狀金屬鐵A之於熔鐵F面的裝入位置 14 201215682 設於電極節圓内。 即，如上所述，先前之還原鐵由於其視密度與熔融炫 潰大致相等’故而投入電弧爐之熔液中的還原鐵於熔融炼 潰層中滯留相對長之時間，並經由熔融熔渣層而藉由電弧 加熱進行熔解。因此，還原鐵之裝入位置並無特別限制。 相對於此，本發明之粒狀金屬鐵A由於其視密度與熔 鐵F大致相等，故而投入電弧爐2之熔液中的粒狀金屬鐵a 會穿透熔融熔渣層E鑽入熔鐵層F中，並經由熔融熔渣層e 與溶鐵層F藉由電弧加熱而熔解。因此，若將粒狀金屬鐵a 裝入自電極7分離之位置，則會產生對粒狀金屬鐵A之傳 熱不足，粒狀金屬鐵A之熔解殘物蓄積於熔鐵層F中之虞。 因此尤其推薦將粒狀金屬鐵A之於熔鐵ρ面之裝入位置 設於電極節圓β ’藉此電弧熱更直接、有效地傳至粒狀金 屬鐵A，防止熔解殘物，使熔鋼G之生產性進一步提高。 又’較佳為將粒狀金屬鐵八之平均粒徑設為【〜⑽mm。 其原因在於：若粒狀金屬鐵A之粒度過小，則於自旋 轉爐床式M i中排出後分別回收時易於混入微細之熔洁成 =吏，分純度下降’或於裝入電狐…時易於飛散而 則二、率下降。另一方面’若粒狀金屬鐵A之粒度過大， 狀：物以下之虞：以旋轉爐床式M 1製造時傳熱至上述塊 部較為耗費時間而使生產性下降，或於爐上料 “時料斗6之流出部發生堵塞，或以電狐爐2 =時：解速度下降。粒狀金屬…更佳平均粒徑為2 ‘）Him 〇 15 201215682 :本發”，所謂平均粒徑係指以筛分法 虞各I 網間之代表徑與其篩網間之質量所算出的灸 粒徑。例如，使用筛網為D,、D2...、Dn、Dn+i(Di<DM <Dn<Dn+1)之筛子進行分級時，化 2<··· 量為^之情形時，質量平均粒徑dm定義為之質 '“ Wk)e於此，dk為筛網D ;广 代表徑，dk= (Dk+Dk+1) /2。 1 間之 又，將粒狀金屬鐵A連續地裝入電弧爐2之熔鐵 時’較佳為-面使形成於熔鐵層F上之熔融熔渣 中 而一直包覆電⑮7之下端—面進行轉。藉此，電^ 不會散逸至上部空間，而可更有效地傳遞至熔鐵層 … 進一步提高粒狀金屬鐵A之熔解速度。㈣料層: 形高度可藉由如下方式而調整：例如於炼鐵層f中吹入： 氣，藉由熔鐵層F中之碳的脫碳反應而生成c〇氣體。氣 又較佳為，在不冷卻至常溫下，將以旋轉爐床式爐丄 所製造的粒狀金屬鐵A於4〇〇〜灣之高溫狀態下連續地 裝入電弧爐2之熔鐵F中。 藉此，可有效地利用粒狀金屬鐵A之顯熱，進而，降 低電弧爐2中之溶解能量之基本單位，並且提高熔鋼〇之 生產性（熔剛生產速度）。 將粒狀金屬鐵A之裝入溫度的較佳範圍設為4〇〇〜7〇() °C之原因在於’係根據如下之理由，，由於就有效利用 粒狀金屬鐵A之顯熱的觀點而言必需某種程度的溫度，故 而下限溫度設為400t，且藉由磁選將粒狀金屬鐵A與熔渣 16 201215682 成分B及底鋪碳材c分離時，必須將粒狀金屬鐵A磁化， 故而將上限溫度設為較鐵之居里溫度（770°c )低的700°c。 為將粒狀金屬鐵A於高溫狀態下裝入電弧爐2中，將 自旋轉爐床式爐1中排出之1〇〇〇〜11〇〇〇c左右之粒狀金屬 鐵A與熔渣B及底鋪碳材c的混合物稍作冷卻以保護後段 之篩網3、磁選機4、輸送機5等設備後，共同以高溫規格 之篩網3與磁選機4將粒狀金屬鐵A分離回收，並將該粒 狀金屬鐵A藉由高溫規格之輸送機5運送至電狐爐2之爐 上料斗6中並暫時儲存，使自該爐上料斗6流出時之溫度 為彻〜70(TC即可。再者，自用以將上述混合物自旋轉爐 床式爐1排出的排出管直至電弧爐2之爐上料斗6為止， 為防止粒狀金屬鐵A與大氣直接接觸而再氧化，可吹入乂 等製成惰性氣體環境。 (變形例） 〃上述實施形態中’作為還原熔融爐之爐形式而例示有 旋轉爐床式爐，但亦可使用直線爐。 又，上述實施形態中，作為含有碳質還原材料與含氧 化鐵之物質的原料，已例示將碳皙 町i買還原材料與含氧化鐵之 物質塊狀化而成的塊狀化物，但亦 I-坏可不經塊狀化而將該等 直接以粉狀使用。 態之粒狀金屬鐵的 亦可使用運送手推 又’上述實施形態中，作為高溫狀 運送裝置已例示高溫規格之輸送機，伸 車及起重機等移送經保溫之容器。 又，上述實施形態中 已例不將旋轉爐床式爐與電弧 17 201215682 置之情形’但於將旋轉爐床式爐與電弧爐分離設 之*月形時1將以旋轉爐床式爐所製造的粒狀金屬鐵冷 部至常溫，則粒狀金屬鐵暫時溶融後固化，因此與還原鐵 相比緻密化，g) |t|_，i f t ， 因此了不採取特別之防止再氧化方法而使 用通常之輸送方法輸送至電弧爐。 又，上述實施形態中，作為初始裝入電弧爐中之其他 鐵原料已例示廢料’但亦可使用還原鐵或粒狀金屬鐵，亦 可將該等2種以上併用。 初始裝入電弧爐中之其 ，亦必須使連續地裝入 之熔鐵中的粒狀金屬鐵 40〜80質量％。換言 再者，於使用粒狀金屬鐵作為 他鐵原料的全部或一部分之情形時 以該初始裝入之其他鐵原料所製作 相對於總裝入鐵原料的使用比例為 於使用粒狀金屬鐵作為初始裝入電弧爐中之其他鐵原 料之全部或—部分之情形時，由於總粒狀金屬鐵相對於總 裝入鐵原料的使用比例為初始裝入量與連續裝入量合計之 比例，故而會為較40〜80質量％更高之使用比例，因此， 必須將該合計比例調整為4〇〜80質量％。 已詳細地又參照特定之實施態樣對本申請案加以說 明’但對業者而言明確可不脫離本發明之精神及範圍而添 加各種變更或修正。 本申請案係基於2010年6月28日提出申請之日本專 利申請案（特願2010— 146114 )纟，且其内容作為參照而 併入本文中。 [產業上之可利用性] 18 201215682 根據本發明，將以還原熔融爐製造之含碳量1 〇〜4.5 質S °/〇的粒狀金屬鐵藉由併用氧氣吹煉而使上述粒狀金屬 鐵中的碳燃燒’並且相對於總裝入鐵原料使用4〇〜8〇質量 %，並將其連續地裝入其他鐵原料初始裝入電弧爐中而製成 的炼鐵中’藉此可實現大幅降低熔解能量且提高電弧爐之 能量效率，並且大幅提高熔鋼之生產性。 【圖式簡單說明】 圖1 ’係表示本發明實施形態之熔鋼製造設備的概略構 成之流程圖。 圖2 ’係表示電弧爐中之粒狀金屬鐵相對於總裝入鐵原 料之使用比例與熔解能量的關係。 圖3 ’係表示電弧爐中之粒狀金屬鐵相對於總裝入鐵原 料之使用比例與熔鋼生產速度的關係。 圖4 ’係表示熔解試驗裝置之概略構成之部分縱剖面 圊。 圖5 ’係表示熔解試驗裝置中之粒狀金屬鐵及還原鐵的 裝入速度與投入電力之關係。 【主要元件符號說明】 1 旋轉爐床式爐 2 電弧爐 3 篩網 4 磁選機 5 輸送機 6 爐上料斗 19 201215682 7 電極 A 粒狀金屬鐵 B 溶漬 C 底鋪碳材 D 廢料 E 熔融溶潰層 F 熔鐵、熔鐵層 G 熔鋼[Table 3] - __J melting material 5G 〇lcg high frequency induction furnace 901 electric arc furnace input power ~ efficiency [C] = [Β] / [Α] χ 1 〇〇 (%) loading speed (kg / min) total loading (kg) Total input electric energy (KWh) Basic unit of electricity [A] (kWh/t) Basic unit of electric energy [B] (KWh) Granular _ Chapter iron 4 29.13 h 20.8 714 366 51.3 7 72.62 42.4 584 366 62.7 13 201215682 Here, the maximum melting rate [R] per MW of the granular metal iron in the present melting test apparatus shown in Table 2 is corrected by dividing the above-mentioned input electric power efficiency [C]/100. The maximum melting rate per MW of input power of the granular metallic iron in the 90 t electric arc furnace actually operated (refer to the "corrected maximum melting speed" column in Table 2 above) is inferred. The above inference results are summarized and shown in the "Continuous Loading" column of Table 4 below. Moreover, in the same table, the carbon content of the granular metallic iron is 2.5% by mass, and the carbon-containing carbon is burned and energized by oxygen blowing, and the granular metallic iron is further heated at 600 ° C. In the case of the high temperature loading, the basic unit of electric power in the 90 t electric arc furnace actually operated above was estimated, and the result of inferring the maximum melting rate per 1 MW of the input power of the granular metal iron was recorded. [Table 4] Power basic unit (KWh/t) Maximum melting speed (Kg/min/MW) Continuous loading 366 [Basic] 44 to 62 Additional continuous loading + C combustion 312 51 ~ 77 Additional high temperature continuous loading + C Combustion 230 70 to 98 According to the results of the estimation shown in Table 4 above, it is understood that the maximum melting rate per MW of input power of the granular metallic iron varies depending on the carbon content or the charging temperature of the granular metallic iron, but In the range of 40~100 kg/min/MW. Therefore, it is recommended to set the charging speed of the granular metal iron A per 1 MW of electric power to 40 to 100 kg/min/MW. Further, it is preferable that the filling position 14 201215682 of the granular metallic iron A on the surface of the molten iron F is provided in the electrode pitch circle. That is, as described above, the previously reduced iron is retained in the molten refining layer for a relatively long time by the molten slag layer because the apparent density is substantially equal to the melting swell. The melting is performed by arc heating. Therefore, the loading position of the reduced iron is not particularly limited. On the other hand, since the granular metallic iron A of the present invention has substantially the same apparent density as the molten iron F, the granular metallic iron a which is put into the molten metal of the electric arc furnace 2 penetrates the molten slag layer E and is drilled into the molten iron. In the layer F, it is melted by the arc heating by the molten slag layer e and the molten iron layer F. Therefore, when the granular metallic iron a is placed at a position separated from the electrode 7, the heat transfer to the granular metallic iron A is insufficient, and the molten residue of the granular metallic iron A is accumulated in the molten iron layer F. . Therefore, it is especially recommended to set the loading position of the granular metallic iron A to the molten iron ρ surface at the electrode pitch circle β′, whereby the arc heat is more directly and efficiently transmitted to the granular metallic iron A, preventing melting of the residue and melting. The productivity of steel G is further improved. Further, it is preferable to set the average particle diameter of the granular metallic iron eight to [~(10) mm. The reason is that if the particle size of the granular metal iron A is too small, it is easy to mix into the fine melting and melting after being discharged from the rotary hearth type M i, and the purity is decreased, or the electric fox is loaded... When it is easy to fly, then the rate is reduced. On the other hand, if the particle size of the granular metal iron A is too large, it is less than the following: it takes time to transfer heat to the above-mentioned block portion when it is manufactured by the rotary hearth type M1, and the productivity is lowered, or the furnace is charged. “When the outflow of the hopper 6 is blocked, or when the electric fox furnace 2 =: the speed of the solution decreases. The granular metal...the better average particle size is 2 ')Him 〇15 201215682 :本发”, the so-called average particle size Refers to the moxibustion particle size calculated by the sieving method between the representative diameter of each I mesh and the quality of the screen. For example, when the screen is classified by a sieve of D, D2, Dn, Dn+i (Di<DM <Dn<Dn+1), when the amount of 2<··· is ^, The mass average particle diameter dm is defined as the mass 'Wk)e where dk is the screen D; the broad representative diameter, dk=(Dk+Dk+1) /2. 1 and then, the granular metal iron A When the molten iron of the electric arc furnace 2 is continuously charged, it is preferable that the surface is formed in the molten slag formed on the molten iron layer F and the lower end of the electric heating 157 is turned over. Dissipate to the upper space and transfer to the molten iron layer more efficiently... Further increase the melting rate of the granular metallic iron A. (4) Material layer: The height of the shape can be adjusted by, for example, blowing in the ironmaking layer f : gas, which generates a c〇 gas by decarburization reaction of carbon in the molten iron layer F. The gas is preferably a granular metallic iron produced by a rotary hearth furnace without cooling to normal temperature. A is continuously charged into the molten iron F of the electric arc furnace 2 at a high temperature of 4 〇〇 to bay. Thereby, the sensible heat of the granular metallic iron A can be effectively utilized, thereby further reducing the dissolved energy in the electric arc furnace 2. Basic order And increase the productivity of the molten steel crucible (melting production speed). The preferred range of the loading temperature of the granular metallic iron A is set to 4 〇〇 to 7 〇 () ° C because the reason is as follows For the reason, since a certain temperature is necessary from the viewpoint of effectively utilizing the sensible heat of the granular metallic iron A, the lower limit temperature is set to 400 t, and the granular metallic iron A and the slag 16 201215682 component B are magnetically selected. When the bottom carbon material c is separated, the granular metal iron A must be magnetized, so that the upper limit temperature is set to be 700 ° C lower than the Curie temperature (770 ° C) of the iron. In the state where the electric arc furnace 2 is placed, the mixture of the granular metal iron A and the slag B and the bottom carbon material c which are discharged from the rotary hearth furnace 1 is about 1 to 11 〇〇〇c. After cooling to protect the screen 3 of the rear stage, the magnetic separator 4, the conveyor 5 and the like, the granular metal iron A is separated and recovered by the screen 3 and the magnetic separator 4 of a high temperature specification, and the granular metal iron A is separated. It is transported to the hopper 6 of the electric fox furnace 2 by the conveyor 5 of the high-temperature specification and temporarily stored, so that the hopper 6 is fed from the furnace. The temperature at the time of the exit is ～70 (TC is sufficient. Further, from the discharge pipe for discharging the above mixture from the rotary hearth furnace 1 to the hopper 6 of the electric arc furnace 2, in order to prevent the granular metal iron A It is re-oxidized by direct contact with the atmosphere, and can be blown into a gas atmosphere to form an inert gas atmosphere. (Modification) In the above embodiment, a rotary hearth furnace is exemplified as a furnace form of a reduction melting furnace, but a straight line may be used. Further, in the above-described embodiment, a bulk material obtained by massaging a carbonaceous material and a substance containing iron oxide as a raw material containing a carbonaceous material and an iron oxide-containing material is exemplified. However, I-bad can be used directly in powder form without lumming. In the above-described embodiment, the high-speed conveyor is exemplified as a high-temperature conveyor, and the vehicle, the crane, and the like are transferred to the heat-insulated container. Further, in the above embodiment, the rotary hearth furnace and the arc 17 201215682 are not provided. However, when the rotary hearth furnace is separated from the electric arc furnace, the rotary hearth furnace is used. When the granular metal iron is produced to a normal temperature, the granular metallic iron is temporarily melted and solidified, so that it is densified compared with the reduced iron, g) |t|_,ift, so that no special reoxidation prevention method is employed. It is delivered to the electric arc furnace using conventional conveying methods. In the above-mentioned embodiment, the waste material is exemplified as the other iron material which is initially charged in the electric arc furnace. However, it is also possible to use the reduced iron or the granular metal iron. It is also necessary to initially charge the molten iron in the molten iron by 40 to 80% by mass. In other words, when granular metal iron is used as all or part of the iron raw material, the ratio of the use of the other iron raw materials initially prepared to the total iron raw material to the total iron raw material is used as the initial use of the granular metallic iron. In the case of all or part of other iron raw materials charged in the electric arc furnace, since the ratio of the total granular metal iron to the total charged iron raw material is the ratio of the initial loading amount to the continuous loading amount, Since the ratio is higher than 40 to 80% by mass, the total ratio must be adjusted to 4 to 80% by mass. The present application has been described in detail with reference to the specific embodiments of the present invention, and it is understood that various changes and modifications may be added without departing from the spirit and scope of the invention. The present application is based on a Japanese patent application filed on Jun. 28, 2010, the entire disclosure of which is hereby incorporated by reference. [Industrial Applicability] 18 201215682 According to the present invention, the granular metal iron having a carbon content of 1 〇 to 4.5 S ° / 〇 produced by a reduction melting furnace is blown with oxygen gas to make the above-mentioned granular metal The carbon in the iron is burned' and is used in the iron making made by using 4 〇 to 8 〇 mass% of the total iron raw material and continuously charging it into other electric iron materials and initially charging the electric arc furnace. The melting energy is greatly reduced and the energy efficiency of the electric arc furnace is improved, and the productivity of the molten steel is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flow chart showing a schematic configuration of a molten steel manufacturing apparatus according to an embodiment of the present invention. Fig. 2' shows the relationship between the ratio of the use of the granular metallic iron in the electric arc furnace to the total iron content and the melting energy. Fig. 3' shows the relationship between the ratio of the use of the granular metal iron in the electric arc furnace to the total iron-loaded material and the production speed of the molten steel. Fig. 4' is a partial longitudinal section 概略 showing a schematic configuration of the melting test apparatus. Fig. 5' shows the relationship between the charging speed of the granular metallic iron and the reduced iron in the melting test apparatus and the input electric power. [Main component symbol description] 1 Rotary hearth furnace 2 Electric arc furnace 3 Screen 4 Magnetic separator 5 Conveyor 6 Furnace hopper 19 201215682 7 Electrode A Granular metal iron B Soluble C Bottom carbon material D Waste E Melt solution Fractured F molten iron, molten iron layer G molten steel
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